In almost all countries including India, the air pollution legislation is based on a certain accepted level of pollutant concentration. To plan and execute air pollution programmes designed to meet the requirements of the legislation, therefore, we may be called upon to predict the ambient air pollutant concentration that will result from any planned activity.

In Unit 7, we will discuss the sources of particulate pollution and particle dynamics, i.e., the motion of particulates under gravity, centrifugal force and electrostatic field. We will then discuss three particulate separating equipment - gravity settling chambers, cyclone separators and electrostatic separators - with illustrations.

Air filters are very efficient units for the separation of fine particles. Indeed, their efficiency of separation is almost 100%, if they are properly designed and operated. If we have to make the stringent requirements of legislation with respect to particulate emissions, then, more often than not, we will have to make use of these devices.

We will discuss the air pollution control aspects of the volatile
organic compounds (VOCs), which are the second most
widespread and diverse class of air pollutants. VOCs can be toxic
by themselves or they can form explosive mixtures with air or
oxygen, and they remain in the atmosphere for a long period of
time. Further, they contribute to the formation of photochemical
compounds (which are ......

We will examine the air pollution control aspects of other two important air pollutants, viz., sulphur dioxide (SO2) and oxides of nitrogen. Sulphur dioxide is formed when a material containing sulphur is burnt and oxides of nitrogen are formed when the bound nitrogen in the material or the nitrogen in the combustion air combines with oxygen at the high temperature of combustion. Note that the hig ......